Canonical Tag

What this check measures

We read `<link rel="canonical">` and verify it exists, is absolute (not relative), points to a non-redirecting URL, and matches the current page or an intentional alternate.

Why it matters

Canonical tags tell Google which URL version is "the" version when content appears under multiple URLs (trailing slash, query params, www vs apex). Wrong or missing canonicals cause ranking to split across duplicate URLs.

Typical findings

• error_outlineCanonical missing entirely — Google picks the URL it sees most often, usually not the one you want.
• error_outlineCanonical points to the homepage on every page — collapses the entire site into one URL for Google.
• error_outlineCanonical uses a relative path — Google requires absolute URLs.
• error_outlineCanonical points to a redirecting URL, confusing the indexer.

How to fix

Set `<link rel="canonical" href="https://...">` on every page, using the absolute URL of the current page (or the intended canonical alternate for duplicates). Next.js has a `metadata.alternates.canonical` field that does this automatically.

Frequently asked questions